Directly calling `extern "riscv-interrupt-{m,s}" fn`... compiles?

[workingjubilee]

I tried this code with rustc --target riscv64gc-unknown-linux-gnu rust_code.rs:

#![feature(abi_riscv_interrupt)]
pub extern "riscv-interrupt-m" fn interrupt_machine() {}

pub extern "riscv-interrupt-s" fn interrupt_supervisor() {}

pub fn main() {
    interrupt_machine();
    interrupt_supervisor();
}

I expected to see this happen: rustc or LLVM reject the direct call.

Instead, this happened:

...wait, why does it compile? This doesn't seem like it should compile...

Meta

rustc --version --verbose:

rustc 1.84.0-nightly (a0d98ff0e 2024-10-31)
binary: rustc
commit-hash: a0d98ff0e5b6e1f2c63fd26f68484792621b235c
commit-date: 2024-10-31
host: x86_64-unknown-linux-gnu
release: 1.84.0-nightly
LLVM version: 19.1.

@rustbot label: +A-hardware-interrupts +A-LLVM +O-riscv +A-ABI +T-compiler

Related Issues

• Tracking Issue for riscv-interrupt-{m,s} ABIs #111889
• Directly calling "x86-interrupt" fn should be invalid #132834

[workingjubilee]

Filed upstream as llvm/llvm-project#115640

[workingjubilee]

#![feature(no_core, lang_items)]
#![feature(abi_avr_interrupt)]
#![no_core]
#[lang = "sized"]
trait Sized {}

pub extern "avr-interrupt" fn avr_interrupt() {}

pub fn call() {
    avr_interrupt();
}

Also compiles...? cc @Patryk27 is this sensical?

@rustbot label: +O-AVR

[workingjubilee]

AVR variant filed upstream as llvm/llvm-project#115641